Geography of the Hirose River
The Hirose River branches away from the Tone River in Shibukawa and flows southeast through the urban area of Maebashi. Its course generally follows the route of the JR Ryomo Line before eventually joining the Tone River again near Sakai-Hiratsuka in Isesaki.
The area near its lower-course confluence is also close to the border with Fukaya City in Saitama Prefecture. The river’s course has been shaped over centuries by changes in the Tone River and by extensive irrigation and water-control works.
Sections Flowing Underground
Some sections of the Hirose River have been converted into underground channels, known in Japanese as ankyo. For example, the river flows underground from the area east of the prefectural sports stadium to the area east of Maebashi Municipal Iwakami Elementary School.
Another underground section is found near Chuo-Maebashi Station of the Jomo Electric Railway, where the construction of the station-front rotary resulted in the river being placed underground.
A River with a Long History
The history of the Hirose River can be traced back many centuries. It is believed that during the medieval period, the main channel of the Tone River flowed through the low-lying area where the present-day Momonoki and Hirose rivers run.
According to local historical accounts, a major change in the course of the Tone River occurred during the Oei era (1394–1427). The river subsequently developed a course closer to its present-day channel.
Fune-tsunagi-ishi: A Trace of the Old River Transport System
One reminder of the river’s former role in transportation is the Fune-tsunagi-ishi, or “boat-mooring stone,” preserved in Chiyoda-machi, Maebashi.
The stone is regarded as a surviving trace of a former landing place where boats were moored. It offers a glimpse into the period when rivers were important routes for transporting people and goods.
The Oldest Written Record of the Hirose River
The oldest known written reference to the Hirose River appears in the Maebashi Fudoki, compiled in 1684 during the Edo period.
The document records that the names Hirose River and Momonoki River were already in use at that time. It also states that the Hirose River was known as Hirinegawa and followed a course broadly similar to its present route.
The document further records that the two rivers originally obtained water from the Tone River through separate intake points. These records provide valuable information about the development of the region’s irrigation system.
Irrigation and River Transportation During the Edo Period
During the early Edo period, river ports such as Maebashi Kawagishi and Isesaki Kawagishi were established. The Hirose River therefore served not only as an agricultural waterway but also as part of the region’s river transportation network.
Originally, the Momonoki River and Hirose River drew water from separate points along the Tone River. However, changes in the riverbed eventually made it difficult to obtain a sufficient amount of water through the Hirose River intake.
In response, a diversion project was carried out at Sannoarai in 1905. Water from the Momonoki River was diverted into the Hirose River, helping to maintain a more reliable water supply for the irrigation system.
The 1947 Typhoon and Reconstruction of the Intake System
A major turning point came in 1947, when the Typhoon Kathleen caused devastating damage to the intake facilities of the Hiromomo Irrigation Canal.
Following discussions about how to restore and improve the system, plans were made to establish a shared intake facility with the Tenguiwa Irrigation Canal, which draws water on the opposite side of the river.
A new facility known as the Bando-Ozeki Joint Intake was constructed in what was then Kitatachibana Village, now part of Shibukawa. Completed in 1951, the facility divided the water into two systems: one serving the Hiromomo Irrigation Canal and the other serving the Tenguiwa Irrigation Canal.
Improvements for a More Stable Water Supply
Further improvements were carried out from 1964 to ensure a more stable water supply. These works included renovation of the intake facilities and extensions to the water tunnels.
Water discharged from the Saku Power Station was also incorporated into the system, while the Bando-Ozeki Joint Intake was retained as a backup facility.
The project was completed in March 1967, establishing a more stable system for supplying water to the irrigation network.
The Hirose River and Gunma’s Hydroelectric Power Stations
The Hirose River has also played an important role in the development of hydroelectric power in Gunma. As part of the Bando Water System Comprehensive Development Project, the Gunma Prefectural Government’s enterprise bureau constructed four power stations along the Hirose Irrigation Canal: Taguchi, Sekine, Koide, and Yanagihara.
Other power facilities were also constructed, including the Maebashi Power Station and the Hiromomo Power Station. These facilities demonstrate how the region’s water resources have been used not only for agriculture but also for energy production.
The Lower Hirose River
South of the Hirose River’s water-control gate near Yanagihara Power Station, the waterway is classified as the Hirose River itself and functions as a tributary of the Tone River.
Farther downstream, the Momonoki River and other waterways join the system before the Hirose River eventually flows back into the Tone River near Sakai-Hiratsuka in Isesaki.
Hirose River Riverside Green Space
Today, the Hirose River is regarded as one of the symbols of Maebashi, a city associated with the phrase “the city of water, greenery, and poetry.” Riverside areas have been developed so that residents and visitors can enjoy the water and surrounding landscape.
Hirose River Riverside Green Space extends between National Route 17 and Chuo-Maebashi Station. The area features greenery, walking spaces, and a monument commemorating the poetry of Sakutaro Hagiwara, one of Maebashi’s most celebrated modern poets.
An Award-Winning Riverside Promenade
The Hirose River Riverside Greenway received the Handmade Hometown Award in fiscal year 1986 in recognition of its contribution to creating a waterside environment where people could interact with nature.
It later received the award’s Grand Prize in fiscal year 2005, reflecting its importance as a public space that combines water, greenery, culture, and community life.
Tributaries and Bridges
The Hirose River is connected to numerous tributaries and waterways. Major tributaries and related channels include the Furo River, Yanagihara Floodway, Sakuma River, Nira River, and Momonoki River.
Numerous bridges cross the river as it passes through Maebashi and Isesaki. Among them are Uchijima Bridge, Taguchi Bridge, Hirose Bridge, Umayabashi Bridge, and Hitone Bridge.
These bridges form part of the everyday landscape of the cities and towns along the river, linking communities while offering views of the waterway.
Power Stations Associated with the Hirose River
Hiromomo Power Station
The Japan Carlit Hiromomo Power Station began construction in December 1952. It was completed in December 1953 and began operations in January 1954.
Gunma Prefectural Taguchi Power Station
The Gunma Prefectural Taguchi Power Station began operation on April 24, 1966.
Gunma Prefectural Sekine Power Station
The Gunma Prefectural Sekine Power Station began commercial operation on May 13, 1967.
Maebashi Power Station
The power station now operated by TEPCO Renewable Power was originally completed by Hirose River Power Company in August 1933, with operations beginning the same month.
On December 1, 1942, it was incorporated into Kanto Distribution Company under the Electric Power Distribution Control Order. On May 1, 1951, it became part of Tokyo Electric Power Company.
Gunma Prefectural Koide Power Station
The Gunma Prefectural Koide Power Station began commercial operation on May 13, 1967.
Gunma Prefectural Yanagihara Power Station
The Gunma Prefectural Yanagihara Power Station also began commercial operation on May 13, 1967.
A River That Shaped the History of Maebashi
The Hirose River is much more than a waterway flowing through Gunma. For centuries, its water has supported agriculture, transportation, industry, and daily life in the region.
Its history is closely connected with the changing course of the Tone River, the development of irrigation canals, the construction of hydroelectric power stations, and the growth of Maebashi and Isesaki.
At the same time, the riverside green spaces of Maebashi have transformed the Hirose River into a place for recreation, poetry, walking, and enjoying nature. For visitors interested in understanding the relationship between water, industry, agriculture, and urban development in Japan, the Hirose River offers a fascinating perspective on the history and landscape of Gunma.